Presentation on theme: "Introduction to Robot Subsystems"— Presentation transcript:
1 Introduction to Robot Subsystems Presented By:Funky Monkeys, Team 846Available online at lynbrookrobotics.comResources > WRRF Presentations
2 Choosing the Right DriveTrain Presented by:Miles ChanI am Miles Chan, and I would like to talk to you about choosing the right drivetrain for your FRC robot. A drivetrain is the system responsible for moving your robot.
3 Drivetrain Requirements Common Features:FastEasy to turnHigh accelerationFIRST Competition Demands:Point-to-point movementTurn in placePush hard
4 Ackerman Steering Team 34’s Design on Chief Delphi Distinction between common for frc and everydayTeam 34’s Design on Chief Delphi
5 Differential/Tank Steering Power left and right sides independentlyFeaturesSimpleEasy to drivePushes hardSwap picture… comment that not only treads we have wheels same concept
6 4 Wheels Differential Steering Wheels slide to turnBt how well does this work???? Lets look at some math.
7 Ability to Turn Turning Torque – Resisting Torque Wheels generate force while friction resistsTurning Torque – Resisting Torque
8 Terminology: µ = Coefficient of Friction Weight = Weight of the robot Track (W )µ = Coefficient of FrictionWeight = Weight of the robotF = ForceT = TorqueWheelbase(L)
9 Maximum Tractive Force Per Wheel (FTMax) Track (W )Wheelbase(L)Let’s say that the maximum tractive force that your robot exerts on the ground is 80 pounds. If your gearmotors can apply 150 pounds of force, what’s going to happen?
10 Maximum Turning Torque (TTMax) Track (W )W/2Wheelbase(L)Loosely speaking, torque is a measure of the turning force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.
11 Maximum Resisting Torque (TResisting) Track (W )L/2Wheelbase(L)
13 4 Wheel Layout Remember: Turning Force – Resisting Force Only wide robots can turnWhat are the disadvantages of having a short wheelbase? How can you have the stability of a long wheelbase with the ability to turn of a short wheelbase?
14 6 Wheel Layout Weight spread over 6 wheels Only 4 wheels resist turningView the slide with the animations.
16 6 Wheels Dropped Center Center wheels dropped about 1/8 inch Improvement of 33% - 100%Rocks on center when turning10%But now lets look at some other ways to make robots turn more easily30%10%
17 2 Wheels, 2 Omniwheels Omniwheels c2 Wheels, 2 OmniwheelsOmniwheels90° rollers allow sideways motionCenter of rotation between non-omni wheels4 wheels provide tractive forceNo Wheels ResistPlease view this slide as it will be animated during the presentation or slide the omniwheel over to see the text.
18 Swerve Drive Wheel modules rotate Advantages Disadvantages Translational movementPushes hardDisadvantagesComplicated designIncreased need for driver trainingRequires additional steering motorCraig Hickman’s Design on Chief Delphi
19 Mecanum Wheels45° Rollers allow lateral movement
24 Conclusion Exotic Drives Tank Drivetrain Cool factor May give key advantage in a particular game.Tank DrivetrainSimple solution - rugged & reliableIrfanview
25 Electrical Subsystem Presented by: The Funky Monkeys Team 846 Akshat Agrawal, Anurag Makineni, and Jackie ZhangElectrical = power distribution + power controlElectronics = low power sensors and circuitsBDCComm
26 Power Distribution Diagram Robot ControllerMake motor in the corner smaller to resemble scalingMake CPU darkerPut red/black lines closer togetherPut currents for the branches – CPU = 20 A, Spike = 20 A, Speed Controller = 40 A,
27 Battery 12V Lead Acid Battery (18Ah) 13 Pounds Provides over 100 amperes of current. Total output of over watts of power.Can supply over 700 amperes of current when terminals are shorted.Explain battery safetyTwo hands because it is heavyNylon stop nut is a tipRemove #10 screw - doneSmaller than a car batteryFix spacingRemove bullet point for take precautionsChange textNEED TO SAYTerminals are separateWrenchWelded together
28 Robot Power SwitchUsed to turn robot on and off, including emergency shut offAlso a 120 amp circuit breakerMust be placed in an accessible locationNot located accessiblyShould be in an easy-to-access areaOn/Off switchFire hazardRetitle to robot power switch120 amp circuit breakerControl should be changed to limitExceed 120 amps and it will breakRemove bullet points when not necessaryHigh current switchHandles high enough currentPrimary importanceDoubles as a circuit breaker
29 Power Distribution Board Main Power Circuit connection20-40 Ampere Fuse LocationBranch circuit power connection
30 DC To DC ConvertersUsed to change voltage coming from battery to specific voltage required in branch circuit12V-5V12V-24V (for robot controller)
31 Power Distribution Diagram 18AWGRobot Controller100A6AWG40A20A12AWG18AWGMake motor in the corner smaller to resemble scalingMake CPU darkerPut red/black lines closer togetherPut currents for the branches – CPU = 20 A, Spike = 20 A, Speed Controller = 40 A,
32 American Wire GaugeSizes are based on the AWG (American Wire Gauge) SystemAWG sizes are based on number of wire draws – Higher gauge = thinner wireExplain safety concerns when using smaller diameter wires
33 CCL Industrial Motors Limited (CIM) Motors (FRC 2011)Name# in KOPAdditional AllowedTotalCIM24BaneBotsFisher Price1Window MotorsWorm GearAutomotive Window MotorReplace with collection of motorsOnly allowed to use motors inside the kitBe aware that the rules may specify that you can buy extra motors (of the same type)Discuss major types of motorsFIX:scaling of picturesMabuchi is the motor on the leftCaptionProperly identify with companiesCIM = CCL industrial motorJohnson electric motors for FPMabuchiCCL Industrial Motors Limited (CIM)RS Series Motor
34 Robot Controller CompactRio National Instruments Embedded Controller The “Brain” of the robotSends control signals to componentsIn 2012, rookie teams will receive new smaller cRIO.Costs $525 for veteran teamsCosts $285 without I/O modulesServo testers at hobby stores to generate control signal for ESCsSpeakingServo is closed loop motor controlExpand ESCFixCPU darkness
35 cRIO Specs 2012 cRIO-4 Slots Power Proccessor Memory Software 24V Power via PD BoardProccessor400 MHzFreescale MPC5125Memory256MB System Memory512MB Storage MemorySoftwareVXWorks Operating SystemLab View, C++, JavaHas an Field Programmable Gate Array (FPGA) allows for real time access to the robot
36 PROBLEM! The cRIO cannot directly control the motors. Solution Cannot provide enough power – will get fried if that much power runs through it.SolutionIntermediary Motor ControllersRelaysElectronic Speed Controllers
37 Spike RelaysRelays close or open the circuit based on signals from the cRIO.Use an H-Bridge
38 How an H-Bridge Works S1+S4 FULL FORWARD S3+S2 FULL REVERSE S1+S3 BRAKES1S3MOTORS2S4Ground
39 Electronic Speed Controller (ESC) Control the amount of power sent to the motors in addition to direction that motor turns.Two types of ESC’s:Victor 884 ESC Jaguar ESC2004+ Victor2009+ Jaguar
41 Pulse Width Modulation (PWM) Pulse Width Modulation is used in two ways on our FIRST Robots:To provide a varying amount of power to the motors.To communicate with the Speed controller.
42 Variable Power Delivery The Speed Controller varies the power delivered to the motors by changing the “Duty Cycle.”DUTY CYCLE (%) = TIME ONPERIOD12V0VDUTY CYCLEPERIOD (ms)12V0V
43 Speed Controller Communications There are two ways to communicate with the ESCCAN-busUses “Message based protocol” (like Ethernet)Servo CableUses Pulse Width Modulation
44 Speed Controller Communications using PWM RC Model Aircraft standard:The width of the pulse is measured as unit of time. Time which each pulse lasts is the pulse width.Signal:2.0 ms = full forward1.75 ms = 50% fwd1.5 ms = off1.0 ms = full reverse1.5 ms0.5 msVoltage applied only 50% instead of powerVariable resistor firstOn and off so no mechanical switchTransistorIntroduce new slide for communication (see bottom of these notes)Remove odd pictureRadio control signal for the VictorDescribe frame from 20ms to 40msPWM communicationImmune to electronic noiseIntroduce slide for communicationSpike with three wires - 3 wire servo cableVictor/Jag use PWM data signal + descriptionJaguar also has data communication port for the CAN-Bus40 ms(20ms-50ms)
45 CAN-Bus “CAN” Stands for “Controller Area Network” Is a single chain of point-to-point connectionsThe “bus” goes around the chain delivering the signal to different addresses – each ESC has its own addresscRIO2 CANESCESCESCESCESCESCESCESC
46 How does the CAN-bus simplify wiring? ESCcRIO2 CANESCcRIO(Daisy Chaining)Although the amount of wires is the same in each case, without the CAN-bus, the wires have to stretch all the way across the robot from the cRIO to each ESC, whereas with the CAN-bus, they are all linked together in a single chain.
47 CAN-Bus Wiring Telephone-style RJ11 instead of servo wire Easy to make custom length with crimp toolCan’t be put in backwardsServo WireCalled servo wire because it is used to connect to the servos of remote-controlled vehiclesNEED TO SAYServo wire coming looseCrimper cheap at Radio Shack/Home DepotTelephone Wire
48 Power Distribution Diagram Robot ControllerMake motor in the corner smaller to resemble scalingMake CPU darkerPut red/black lines closer togetherPut currents for the branches – CPU = 20 A, Spike = 20 A, Speed Controller = 40 A,
49 Sensors and Electronics Presented by:Brian AxelrodManual vs Automation
50 Sensors and Electronics Presented by:Brian AxelrodManual vs Automation
59 Pots: Uses Sense position: e.g. lift How to sense the lift position? Travel length is 6 feetNo linear pot long enough
60 Multi-turn Pots Multi-turn pot: Alignment is important! Usually 3, 5, or 10 turns$$Alignment is important!Continuous rotation: use encoderMove pot picture
61 Reading the Value Analog voltage level Analog-to-Digital Converter (ADC)Converts to numberfor 10-bit ADCComes in kop with cRio as analog module 8 portsEasy to implement in codem_liftPot.GetAverageValue()
62 Optical Encoders to controller Optical Sensor (A) to controller Optical Sensor (B)to controllerImprove animation and show waveformAngles?More than one tickDirectionsSpin animationA ChannelB Channel
63 Optical Encoders to controller Optical Sensor Optical Sensor Brush overJust more ticksRemove optical sensorOptical Sensorto controller
64 Optical Encoders Determining Distance Travelled Determining Speed Count pulsesDetermining SpeedDistance over timeTime over distanceDo in one slide just say two different ways
65 Other Encoders Our 2006 robot’s ball launcher Hall Effect Sensor, and embedded magnet in wheelOur 2006 robot’s ball launcherMake your own encodersDon’t need quadratureusing encoder as a speed sensor
66 Yaw Rate Sensor/Gyro Also commonly known as a gyro Indicates rotational velocity
67 Accelerometer Measures acceleration Detects gravity Going above max acceleration will give you wrong readingsDetect if going up a bump straight
68 Sensing Distance: Ultrasonic Sensors Determine distanceSend pulse of soundMeasure time until echoCONS such as sensitivity to soft and irregular surfacesNoisy environment may cause problems
69 Infrared Proximity Sensors Determines distance to object in front of itAnalog voltage readingvs. ultrasound:Shorter rangeMore accurateSensing game pieces inside your robotShort range non contact sensing
70 Camera Not a magic bullet Can choke your machine Image processing Can sense enviromentCAUTION
71 Kinect Still not a magic bullet RGB-D With proper processing easier to make reliableDepth image not dependant on lightingCAUTION
72 Conclusion Never rely on the operator to do the right thing Useful for adding functionality and as safety featuresLarge variety of sensors that can detect a variety of parametersCan buy sensors atTrossen roboticsDigi-keyMouserAcroname
73 Pneumatics Michael Lin and Eric Yeh presents… Presenter: Michael Lin + EricEY: Hello My name is EricML: Hello My name is Michael, and we are here today to talk about the pneumatics subsystem.
74 Pneumatics - Definition Pneumatics is the use of pressurized air to achieve mechanical movementPresenter: Michael LinPneumatics is commonly confused with hydraulics.- Difference = pneumatics uses are and Hydraulics uses oil. Key difference FIRST does not allow use of hydraulics. But they do allow use of pneumaticsDrillNail gunJack HammerPneumatics?
75 Overview of Pneumatics Presenter: Michael Lin-compressor generate pressure-actuator transform pressure to motion-solenoid controls the motion-tubings and fittings to let the air flow-above is everything we need, to generate motion, but it is not safe and reliable-regulators are used to transform stored air pressure to working pressure-value for safety, is the pressure’s sensor which if sense too much pressure it will release the air, so the system won’t explode
76 From FIRST pneumatics manual Presenter: Michael LinLets start with what powers the entire system; the compressor.From FIRST pneumatics manual
77 Compressor Source of energy in pneumatic system Compacts air Can Generate up to 120 PSICompacts airPresenter: Michael LinThis is the Compressor (Denver Gardner Thomas pump) that FIRST provides to rookie teams. This is what gives the pneumatic system its energy by compacting air.Diaphragm compressor, axial compressor (turbine), piston compressor
78 Diaphragm pump Presenter: Michael Lin DEMO notes: Lets see the pump in action. What we have here is your typical compressor that’s powered by a battery. This is the output of the compressor, and when I turn this plug valve to seal this port, we have an enclosed space that the compressor pumps air into. *hits the switch* This pressure gauge here indicates the pressure at the output of the compressor. When the pressure of the output has reached a certain limit, typically 120 psi, this electrical pressure switch here would open, and that would turn off the compressor. You can hear the compressor pulsing every now and then. We unfortunately have small leaks in the system that vents pressurized air. When this pressure switch detects that the pressure has dropped below a certain value, typically 115 psi, it would close and turn the compressor back on.
79 From FIRST pneumatics manual Presenter: Michael LinLets start with what powers the entire system; the compressor.From FIRST pneumatics manual
80 Common Valves and Fittings Pressure switch, Release valve, Plug valve,Presenter: Michael LinNotice this cylinder. On this end it has a common L join, but the one on this side has a screw on top. This is a flow-rate valve. <explanation> Because of this, you can fit two of these valves on the cylinder and that allows you to independently control the extending and retracting speeds.*Make sure to make it a point that a team will only need to use on type of valve. All valves here are just types of valves that can be used.
81 From FIRST pneumatics manual Presenter: Michael LinNow lets say we want 60 psi but from before we know that if we feed the pressurized air directly to the system we would be outputting more than that. How would we achieve this daunting task? By adding a regulator!Now that we see the basics behind pneumatics, we want to know how to usefully incorporate it into our robot when we’re designing it. To do this, we need to control several factors that affect the mechanics of actuators. The first factor is output pressure.From FIRST pneumatics manual
82 Regulator Maintains a constant level of pressure. Working air pressureMaximum of 60 psi for FIRST competitionsPresenter: Michael LinYou can see here that the pressure at the output of the compressor is at 120 psi, but FIRST only allows us to operate our actuators at a maximum of 60 psi. We achieve this pressure drop by using a regulator. It drops the input pressure to an output pressure that you can set by turning this knob. This gauge above the regulator shows pressure that being outputted.
83 From FIRST pneumatics manual Presenter: Eric YehNow lets see where the energy of the compressed air is used to get mechanical motion. It’s achieved through these objects, called actuators.From FIRST pneumatics manual
84 ActuatorsActuators convert the difference in air pressure to mechanical motionTakes the working air and makes it into mechanical motionLinear actuators (also known as cylinders)Narrower actuators move more quicklyPresenter: Eric YehAn important note to remember is that the actuator applies full force when the piston isn’t moving.
85 From FIRST pneumatics manual Presenter: Eric YehNow that we see the basics behind pneumatics, we want to know how to usefully incorporate it into our robot when we’re designing it. To do this, we need to control several factors that affect the mechanics of actuators. The first factor is output pressure.From FIRST pneumatics manual
86 Solenoid Valves Controlled by the robot’s CPU Solenoids opens a port to pressure when a voltage is appliedDouble solenoids controls two portsWhen one port is open, the other is closedPresenter: Eric YehYou see how we controlled which way the cylinder moves with a click of a button. Often times we also want to control when we send compressed air to the cylinders or through which ports. For example, suppose you have a pneumatic pistons that you want to use a cylinder to lift something at the finale. We do this with electric solenoid valves. Although these valves are controlled electrically by the robot’s CPU, they can also be mechanically operated by pressing these buttons. A single solenoid valve allows you to open one port of a cylinder to pressure when voltage is applied, or when I press this button, causing the cylinder to either extend or retract. When voltage is no longer applied, the valve releases the pressure to atmosphere, and whatever load is on the piston will cause it to return to its original position. A double solenoid valve allows you to use the cylinder in both directions. When I press this button or when voltage is applied to this solenoid, the valve would open the blue side to atmosphere and the white side to pressurized air, causing the cylinder have an extending force. When the other solenoid is activated, the white side is open to atmosphere and the blue side to pressurized air, causing the cylinder to have a retracting force.Festo single solenoid valveFesto double solenoid valve
87 From FIRST pneumatics manual Presenter: Michael LinWhen we try and apply pneumatics to our FIRST Robots we can not have a compressor on the robot compressing air constantly to meet our demands. So how can we get compressed air on our robots? We use tanks to store the air we need!we want to know how to usefully incorporate it into our robot when we’re designing it. To do this, we need to control several factors that affect themechanics of actuators. The first factor is output pressure.From FIRST pneumatics manual
88 Tank Tanks are a reserve of compressed air Maximum of 120 psi for First competitionsPresenter: Michael LinPlastic vs. Metal = weight concernHow many movements can we do with one tank?
89 Finding Linear Force 𝐷 Presenter: Eric Yeh What is area – pi x radius squaredWhat is pressure – force divided by areaWhat is force – pressure times areaLets calculate the amount of force which will be needed…89
90 Finding Linear Force 𝐷 𝑑 Presenter: Eric Yeh What is area – pi x radius squaredWhat is pressure – force divided by areaWhat is force – pressure times areaLets calculate the amount of force which will be needed…𝑑90
91 Finding Linear Force 𝐷 𝑑 Presenter: Eric Yeh What is area – pi x radius squaredWhat is pressure – force divided by areaWhat is force – pressure times areaLets calculate the amount of force which will be needed…𝑑91
92 Forces of Different Bore Cylinders at 40 psi and 60 psi Bore (inches)0.751.502.00Extending (40 psi)18 lbf71 lbf126 lbfRetracting (40 psi)16 lbf65 lbf113 lbfExtending (60 psi)26 lbf106 lbf188 lbfRetracting (60 psi)24 lbf97 lbf170 lbfPresenter: Eric YehWasn’t doing all that math fun!? Well here is a table with basic numbers so you don’t need to do all that math again.From FIRST pneumatics manual
93 From FIRST pneumatics manual Presenter: Michael LinWhen we try and apply pneumatics to our FIRST Robots we can not have a compressor on the robot compressing air constantly to meet our demands. So how can we get compressed air on our robots? We use tanks to store the air we need!we want to know how to usefully incorporate it into our robot when we’re designing it. To do this, we need to control several factors that affect themechanics of actuators. The first factor is output pressure.From FIRST pneumatics manual
94 Finding Linear Force 𝐴𝑟𝑒𝑎=𝜋 ∗𝑟 2 𝐷 𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒= 𝐹𝑜𝑟𝑐𝑒 𝐴𝑟𝑒𝑎 𝐴𝑟𝑒𝑎=𝜋 ∗ 𝑑 2 2 𝐴𝑟𝑒𝑎=𝜋 ∗ 𝑑 2 2𝐹𝑜𝑟𝑐𝑒=𝑃𝑟𝑒𝑠𝑠𝑢𝑟𝑒∗𝐴𝑟𝑒𝑎𝐴𝑟𝑒𝑎= 𝜋 4 ∗ 𝐷 2𝐹= 𝜋 4 ∗𝑃 𝐷 2Presenter: Eric YehWhat is area – pi x radius squaredWhat is pressure – force divided by areaWhat is force – pressure times areaLets calculate the amount of force which will be needed…𝐹= 𝜋 4 ∗𝑃 (𝐷 2 − 𝑑 2 )𝐴𝑟𝑒𝑎= 𝜋 4 ∗ (𝐷 2 − 𝑑 2 )𝑑94
95 Conclusion Covered major components of FIRST robots Slides available at lynbrookrobotics.comResources > “WRRF Presentations”
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